PRB: SQLCancel Instead of SQLFreeStmt Causes a Memory Leak

 Last reviewed: December 17, 1996
Article ID: Q159571
The information in this article applies to:
  • Microsoft SQL Server, versions 6.0 and 6.5
  • Microsoft Open Database Connectivity, version 2.5
  • Enterprise Edition of Microsoft Visual Basic for Windows, version 4.0

SYMPTOMS

If an ODBC application uses SQLCancel instead of SQLFreeStmt to close an ODBC cursor after some data has been processed, the ODBC cursor library version 2.5 may generate a memory leak.

A Visual Basic 4.0 application may encounter this problem if the application uses the Requery method of an RDO Resultset. The ReQuery method internally invokes SQLCancel instead of SQLFreeStmt and SQL_CLOSE to close the statement handle, before binding the parameters and results.

CAUSE

An ODBC application should only call SQLCancel when dealing with asynchronous processing. ODBC applications should always use SQLFreeStmt and SQL_CLOSE rather than SQLCancel to close the statement handle.

For more information on how to use SQLCancel, please refer to Microsoft ODBC 2.0 Programmer's Reference and SDK Guide.

MORE INFORMATION

A Visual Basic application can call the Close and OpenRecordset methods instead of ReQuery. The Close method invokes SQLFreeStmt and SQL_CLOSE to close the statement handle.

KBCategory: kbusage kbother
KBSubcategory: SSrvProg
Additional reference words: 2.50 4.00 6.00 6.50

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Last reviewed: December 17, 1996
© 1998 Microsoft Corporation. All rights reserved. Terms of Use.